Why are my July 68 t1221’s slightly quieter/cleaner than my Aug 68 t1221’s ??

[79 2203]

Same 102 003 cones.
Both in 68 straight cabs.
Same guitar.
Same amp.

But the July cab is a little quieter and cleaner.
There are some differences. The August cab is on the floor while the July is on casters, and being on the floor gives it more bottom end, but the July cab is way more mid focused and I would have thought a mid heavy sound would be louder than a bassier sound ??
Also, the Aug cab has been restored with salt n pepper basketweave while the July cab has a nearly see-through thin black cloth. All things equal, shouldn’t the thicker basketweave be quieter ??
The July speakers are all labeled 20 watts. I realise by July they were only making 25 watters, but could they be actual 20 watters ?? Could that explain the difference rather than say how much, or how hard they were played. Assuming they both are the same watts, could there be any differences in manufacturing or materials ?? Same voice coils ??
I mean I can turn up the vol slightly on the July cab and the differences become negligible so it’s absolutely not an issue. Both cabs sound fantastic, but I find this stuff fascinating.

 

[racerxrated2]

If the mids in the July cab are very noticeably different, then I'd say there's a good chance you may have the earlier paper voice coils. Only way to tell, is to remove a speaker and carefully remove the dust cover to see the color of the coil. Bygone tones has good pics as to the color differences between the 20/25w coils.

 

[Brewster]

I wonder if its how both cabinets had been used or broken in. Since it appears to late for white 20 watt coils its the only thing I can think of myself. Im sure they'll be some other input on this to review though. I know, I love my early 68 cabinet compared to my 72 or 78 which both sport t1281 30 watt speakers

 

[Kuga]

I had two '98 Marshall 1936 lead cabs (G12-75T). I bought It new. Still I have one but with '89 G12-75T on It. They sounded different. Same flavor but a bit different.

 

[79 2203]

Thanks guys. Since I posted this I’ve compared the two cabs many more times and the differences are quite shocking. But I’ve used those differences to my advantage by pairing it with the right amp.
The biggest success is with my stock 79 2203 as the July 68 cab smoothes the top end, adds needed midrange, and tames the tendency for boomy bass. Also crazy how much more vintage it makes the sound.
But it’s also works with my stock 70 Super Bass. Not so much for the top end, but more by adding midrange and cutting the amps ample bottom end. And because the cab is so much quieter it really helps tame the 1992’s massive vol. I mean I’m taming it with a Hotplate at -8 or -12db, but if I play it through the Aug cab at -8db it’s noticeably louder, and with the 77 slant with 55hz/30 watt Blackback and V30 cab it’s just too loud for comfortable playing.
OTOH, with my stock 71 1987, the amps aggressive high mids means the July cab can be a challenge to dial in.

So Captain Obvious, but cabs can make a huge difference.